Despite significant improvements in the management of ovarian cancer, approximately 13,900 women per year in the United States are expected to ultimately fail standard therapies and die. For the treatment of ovarian cancer, the broadly used adenovirus type 5 (Ad5) gene therapy vectors have two significant disadvantages: 1) Inadequately efficient or specific gene transfer to ovarian cancer cells and 2) Pre-existing neutralizing antibodies to Ad5-based vectors are often present in 40-60% of the human population. We have recently overcome the first disadvantage by creating an Ad5-based vector targeted to the alphavbeta3 and alphavbeta5 integrin receptors (alphavbeta3/5) that are highly expressed in ovarian cancers. Our results demonstrate that this alphavbeta3/-targeted vector is highly efficient and specific in gene transfer to tumor cells present in the peritoneal cavity. Moreover, we demonstrate that expression of tumor necrosis factor-alpha (TNF) from the alphavbeta3/5-targeted vector has an improved safety profile and enhanced anti-tumor activity compared to a standard, untargeted Ad5 vector. However, preliminary data show that efficient in vivo tumor delivery by the targeted vector is severely compromised by preexisting immunity to Ad5. In the proposed phase I studies we will overcome the disadvantage of preexisting immunity to Ad5 by generating vectors based on adenovirus type 35 (Ad35), for which only a small fraction of the human population has pre-existing immunity. The overall goal of this SBIR is to incorporate the previously tested and efficient tumor targeting and tumor killing elements into an Ad35- based vector to develop a new treatment for ovarian cancer. In the phase I portion of this SBIR, a lead will be generated and tested for (possible) advancement to clinical trials. We will construct an ava3/5 integrin-targeted, Ad35-based vector. To qualify as a lead, the alphavbeta3/5 integrin-targeted, Ad35- based vector must meet predefined milestones for delivery and safety (Specific Aims 1 and 2, Year 1) and anti-tumor activity (Specific Aim 3, Year 2) in the presence of pre-existing neutralizing antibodies to Ad5.